Nothing wrong with either of these saws! The 350 is more pro grade than the 250, however, the 250 is a pretty good saw. The #2 sold Stihl behind the MS290 and new are now $329. 1/2 that for a used saw in running condition, maybe a little more in great condition. I'm selling one with little time on it for $200 and have turned down $150 three times, $175 it would go.
The Husky 350.... very nice and they sell in my area for $175-225 all day long. Muffler mod either and you'll be surprised at the power, both pretty light in the hand.... .4lbs you'll never feel the difference. Put a 346 top end on the 350 and you'll have a ripper!
My vote is the 350 because of the 346 upgrade possibility... All magnesium case and a whole lot easier to work on.